Cracking and extracting hydrocarbon oils with a selective solvent



Sept. 27, 1938. E. F. ENGLISH 2,131,169 CRACKING AND-EXTRACTINGHYDRCARBON OILS WITH A' SELECTIVE SOLVENT Filed Nov. 21, 1954 2Sheets-Sheet 1 PA R T/A A -n t: .BUBBL-A.

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Sept. 27, 1938. l F. ENGLISH v 2,131,169

CRACKING AND EXTRACTING HYDROCARBON OILS WITH A SELECTIVE SOLVENT FiledNov. 21, 1934' 2 sheets-sheet '2 f 72d v www H- Gf 9 2 f CooLL-:n

t oaLen RATP/IVA TE LINE 7b2 A c T/o/vA rf/v'a To WE E A Cou/V752CQPRENT SEPARATOR ExmAdv-lo/v Towel COIL .SGLVENT' Ll E l I '-vL 2 60Patented Sept. 27, 1938 7 UNITED vSTATES CRACKING AND EXTRACTINGHYDROCAR- BON OILS WITH A SELECTIVE SOLVENT Edward F. English, BatonRouge, La., assignor to Standard Oil Development Company, a. ccrporationof Delaware Application November`21, 1934,'$erial No. '154,026 1 claim.(c1. 19d-5o) This invention relates to a process of treating hydrocarbonoils, such as the various mineral oils including petroleum oils, shaleoils, oils ob'- tained in the low temperature carbonization ofv coal,hydrogenated Aoily products, etc. by the combination of a cracking and asolvent extraction process, and will be fully understood from thefollowing description when read in conjunction with the drawing, thesole figure of which is a diagrammatic side elevation partly in sectionof an apparatus appropriate for carrying out the invention.

The main object of the present invention is to ysubject the hydrocarbonoil to a cracking process, to separate a cycle stock from the crackedproducts, this cycle stock being a distillate product boiling higherthan the naphtha obtained in the cracking process, to subject this cyclestock to a treatment with a selective solv vent for separation thereofinto a more parafnic and a less paraiiinic product, and to subject thesetwo products to dierent kinds of treatments.

Referring now to Fig. 1, the same will be described in conjunction withthe method of op- 'erating the apparatus illustrated. The fresh feed,such as for example, gas oil, is pumped from storage tank I throughpartial condenser 2 and heat exchangers 3 and 4 into the accumulator 5.The raiilnate from the solvent extraction step is also passed into theaccumulator, as will be described hereinafter. 'Ihe mixed feed from theaccumulator is fed through high pressure intercondenser 6 and heatingcoil 1 into the soaking drum or reaction chamber 8. The mixed 36 feed isheated' to the cracking temperature in coil 1 and undergoes the desiredextent of, crack` ing in the soaking drum 8. A limited amount ofcracking usually takes place in the heating coil. Ifdesired, the soakingdrum may be omitted 4l) from the circuit, the coil temperature beingraised to increase cracking in the heating coil and compensates for lossof cracking in the soaking drum. The cracked eiiiuent from 8, afterpartial release of the pressure, is discharged into 45 the separator 9which may be provided with various fractionating devices, such as discsand doughnuts. Tar is withdrawn from the separator through cooler IIIinto a storage tank (not shown). Vapors from the separator ipass 50through the high pressure intercondenser 6 and,

y through heat exchangers 3 and 4 into the lower part of a. bubble towerII. Part of a heavy cycle stock condensed in intercondenser 6 and/orpart of the cycle stock from heat exchangers 3 and 4 55 may either bereturned to the separator 9 or withdrawn from the unit-through cooler I2or passed to a solvent extraction unit. The bubble tower Il is providedwith eiilcient fractionating means, such as bubble cap plates, andserves for the separation of the naphtha with the `desired endpoint asoverhead product. The naphtha vapors are passed through the partialcondenser 2 and final condenser I5, into the receivers I6- Ia, providedwith vents for the release of gases through lines I1 and I8. Part of thenaphtha is returned to the top of the bubble tower II through line I 1aas a reux for the control of the fractionation. The liquid productobtained at the bottom of the bubble tower II is a cycle stock which isrun through heat exchanger I9 and cooler I9a into the mixing tank I4 ofthe extraction unit. As cooling medium in cooler I9a water or chilledbrine or other suitable cooling medium may be used to reduce thetemperature of the cycle stock from bubble tower II to below that atwhich cycle stock and solvent are completely miscible. The temperature'at which extraction is carried out is selected'to give the desiredcharacter of extract and/or raiiinate. The selective solvent fromstorage tank 20 `is passed to the mixer I4 and thoroughly admixed withthe cycle stocks, after which the mixture is forwarded to the settlingtank 2| in which separation into two layers, 'viz, railnate layer andextract layer takes place. The/so-called raffinate layer consisting ofthe more parainic constituents of the cycle stock together with somedissolved solvent, is reheated in reboiler section 22 arranged in thesaine furnace as heating coil 1, and then discharged into the strippingtower 23 on which a vacuum is preferably maintained. The selectivesolvent is` obtained as overhead vapor condensed in condenser 24 andreturned to the selective solvent tank 20. The solvent-free raiiinate isthen passed to fthe accumulator 5 for recracking. Alternatively, all orpart of the raiiinate may be removed from the system through line 25into a storage tank (not shown) and used for themanufacture of Dieseloil, heating oil or similar products. -The extract layer which consistsof the selective solvent and non-paraiiinic constituents extracted fromthe cycle stock is reheated in heat exchanger I9 and then passed throughthe release valve 26 to tower 21. -In this tower the selectivesolauxiliary cooler subsequent to condenser 28 to further cool solventbefore return to mixer Il.

The extract removed as bottoms from tower 21 is introduced into thevacuum stripper 29 in which the remainder of the selective solvent isremoved as overhead product condensed in condenser 30 and returned tothe storage tank 20. 'I'he extract is removed from the bottom of thestripper 29, cooled in cooler 8| and then passed to `a storage tank 34for various uses to be explained further below. Alternatively, theextract may be subjected to cracking under conditions different fromthose used in the cracking of the mixed feed. Other methods of utilizingthe extract are shown diagrammatically'and consist of either submittingthe same to hydrogenation in the hydrogenation unit 35 or to a chemicaltreatment in the chemical treatingunit 36.

Referring to Figure 2, fresh feed is withdrawn from tank 50 by means ofpump l5I and forced through heating coil 52 in furnace 53. The heatedoil is then passed through line 54 into a separator 55 fromV which theheavy tarry products are withdrawn through line 56'. vapors ,fromseparator 55 are withdrawn through 58, from which gasoline vapors areremoved through line 59, passed through a cooler Sllandk thence passedthrough line 6| into a gasoline storage tank 62. 'I'he heaviestfractions in tower 58 are withdrawn through line 63. An intermediatefraction or cycle oil is withdrawn from tower 58 through line 64 andintroduced into a countercurrent extraction tower 65. A suitableselective solvent contained in storage tank 65, is withdrawn by means ofpump 61 and forced through line 68 into the top of tower 65. Rainate isremoved from tower 65 through line 68 and introduced into a still 10 inwhich the hydrocarbons are distilled from the solvent in the event thatthe solvent used is higher boiling than the hydrocarbon fractions. Itwill be understood that if the solvent used is lower boiling than thehydrocarbons, the solvent will be distilled from the hydrocarbons instill 10. The hydrocarbon vapors are removed from still 10 through line1l and after passing through a vcooler 12, are passed through line 13into the fresh feed tank 50. The solvent is removed from st ill 10through line 14 and returned to the solvent supply tank 86. A

The extract is removed from tower 65 throug line 15 and introduced. intoa still 16 in which the solvent is separated from the hydrocarbons bydistillation. As indicated above, if the solvent is higher boiling thanthe hydrocarbons, the latter will be vaporized, and if the solvent islower boiling than the hydrocarbons, the solvent will be vaporized. Thehydrocarbon vapors are removed from still 16 through line 11 andcollected in extract storage tank 18. The solvent is removed from still15 through -line 19 and returned to the solvent supply tank 66.

The extract is Withdrawn from tank 18 by pump 80 and passed through line8| into a second heating coil 82 in furnace 83, wherein the extract iscracked at a higher temperature than the fresh paraiiinicfeed oil inheating coil 52. The heated oil from coil 82 is passed through line 84and merges with the heated oil from coil 52 flowing through line 54.

The selective solvent may be any of those known to be effective in theseparation of a hydrocarbon oil 'into more parailinic and less The'parafllnic constituents. Usually the extract removed by the selectivesolvent contains the unsaturated naphthenic and aromatic constituents,while the raffinate consists ofthe more parafllnic constituents. We maycite phenol, the several cresols, aniline, furfural, nitrobenzene,triphenyl phosphate, triorthocresyl phosphate, liquid sulfur dioxide,etc. as examples of selective solvents which may be used in the carryingout of the present process. Instead of one solvent a mixture of them maybe used; for example, a mix-v ture of phenol with cresols. The action ofthe selective solvent may also be modified by the addition of otherorganic or inorganic solvents such as, for example, water, alcohols,glycol, etc. 'I'he `extraction step consists of mixing the cycle stockto be extracted with, say, an equal volume or more of the selectivesolvent, thoroughly agitating the mixture, then allowing separation oftwo layers to take place at a temperature below extract layer are thenseparated from each other and the selective solvent is removed from bothlayers, usually by means of distillation, but other means, eitherphysical or chemical, may also be used.

The cracking part of the present process may be carried out in theliquid phase at a pressure of several hundred pounds per square inch,say between 250 and 1,000 pounds per square inch, or even at pressureshigher than that, or in the vapor phase at comparatively low pressuresapproaching atmospheric pressure. The temperature may be any of theusual cracking temperatures or may be considerably higher than say1,000c F. although, in many cases, it is preferred to carry out thepresent process at medium temperatures, say between 800l,000 F, Thearrangement described above and illustrated in the drawing is a tube andtank cracking system, but other systems may also be used. Further, thearrangementl shown may be modified in various ways; thus, for example,when the fresh feed is a dirty stock, such as a topped crude, it mayfirst be preheated and then fed into the separator 9 Ainstead of intothe accumulator 5.

The raiiinate is usually returned to the cracking system as a cyclestock and fed for this purpose into the accumulator 5. However, part orthe whole of the raffinate may be removed and used for various purposes,suchas Diesel fuel, heating oil, furnace oil, etc. The extract may besubjected to cracking under conditions different from those used in themain cracking system composed of heating coil 1 and soaking drum 8.jected to hydrogenation or to various chemical treatments thus, forexample, it may be treated with sulfur for the preparation of woodpreservatives, fngicides and insecticides. It may also be treated with`,various inorganic oxides or sulfides; for example those of arsenic,zinc, mercury, etc. for the same purposes.

By the present process the cycle stock is separated into arafiinateuwhich shows improved characteristics for certain uses such as,for example, Diesel oil and an extract which again is a more appropriateraw material for certain other uses than the untreated cycle stock. Toillustrate the point the extract is a better raw material for treatmentwith sulfur than saturated hydrocarbons, because the latter produce alarge amount of H2S in their reaction with sulfur. The extract is alsoan excellent raw ma- It may also be withdrawn and subin the presence ofa catalyst and in a vapor phase at temperatures between 950-1050 .F.whereby a naphtha having excellent solvent qualities is obtained.

- The following examples are given to illustrate the above: v

1. A paraiiinic gas oil is cracked, the products being gasoline, fueloil, gas and cycle stock. The rst three are withdrawn from the unit, thecycle stock is subjected to'soivent extraction with a mixture of phenoland glycol and separated into rainate and extract. The ralnate issuitable for cracking with a relatively high gasoline yield and istherefore mixed with fresh feed and returned to the cracking process.The extract is suitable for the production of high octane blending stockand is cracked at high temperature in the separate crackling circuit32-33, the distillate from which latter cracking may be blended with theprimary cracking products or may be segregated for use as blending stockto improve the octane number of other distillates. g.

2. 'I'he parafllnic gas oil may be cracked and separated into raffinateas Vin Example 1, the rainate being returned with fresh feed to thecracking process. The extract being more reactive chemically than eitherthe fresh feed or the ramnate is submittedl to sulfurization orarsenication.

3. The c gas oil is cracked and therafvflnate is returned to cracking asabove. The

, cracking stock or high grade Diesel fuel. 1f subjected to destructivehydrogenation in the presence of a catalyst at a temperature of saybetween 950 and 1050 F., it will yield solvents and `toxic oils, theformer suitable` for the preparation of varnishes and the latter for useas wood preservatives, disinfectants and as raw materials for thelmanufacture of explosives and dyes.

The following specific example will illustrate my invention: 18,750gallons per hour of 30 A. P. I. gas oil (completely miscible withaniline at 175-185 F.) fresh feed are passed into the accumulator 5,after being preheated in 2. 3 and I to about 500 F. The mixed feed ispumped from the accumulator at a temperature of about 440 F. and afterbeing preheated in the high pressure heat exchanger 6 to about 540i F..it is passed through the heating coil 1 at the rate of 25,000 gallonsper hour and then through the vertical'soaking drum l in downwarddirection. The cracking stock is heated in the coil to a' temperaturebetween 900 and 930 F. and a pressure bf between 250A and 1,000 poundsper square inch is maintained on the Isoaking'drum. The

separator is 'under a pressure of 10o-150 pounds lsure oi .95 to 145pounds per square inch, the

temperature at its top between 40o-450 l". and at its bottom betweenS-680 F. 'lha distillata mixed product containing gasoline and cycleoil.

ond-meitioned cracking step with the products obtained is approximately6,550 gallons per hour. 3150 gallons per hour of gas are obtained fromwhich 1315 gallons of gasoline and 1835 gallons per hour of .strippedfuel gas are produced. The cycle stock is submitted to a selectivesolvent treatment (withrphenol) as a result of' which there is obtainedafter the removal of the selectivesolvent, 6250 gallons per hour4 oframnate the presence of a sulfactive catalyst at a temf perature of750850 F. and a pressure of 3000- 3500 pounds per` square inch. Thereare obtained 7000 gallons per hour of overhead product separable bydistillation into 4500 gallons per hour of 400 F. endpoint gasoline and2500 gallons per hour of an excellent grade of water white. distillateof 3840 A. P. I. gravity and.. above the boiling range of gasoline. Thegasoline o-b. tained is of 56-60 octane number by the Co-operative FuelResearch Motor Method and highly susceptible to improvement of octanenumber by the addition of tetraethyl lead. Alternatively they 'extractmay be subjected to sulfurization or other chemical treatment.

My process may be modified in various ways. Thus,for example, differentsolvents may be used according to thevmiscibility of the fresh feed withaniline.` In the foregoing specific example the cycle stock subjected toextraction with phenol is such that separation of the rafiinate and thephenol-extract mixture takes place at a temperature above the freezingpoint of phenol. If the fresh feed'is misclble with aniline at arelatively low temperature and the cycle stock subjected to extractionis completely miscible with phenol at the freezing point of the phenol,then a solvent of lower freezing point such asaniline may be used. Bythe addition of a seoond storage tanld similar tostorage tank 20, eitherof the two solvents may be kemployed according to the character of thecycle stock to be subjected to extraction. Y. f

Many other changes and modiiications of myprocess willbe apparent tothose skilled in the art and the same is not to be limited by the specicexample given for illustration but only by the following claim in whichit is my intention to claim all novelty inherent in the invention.

What I claim is: l

'Ihe process of converting a Zas oil .into hydro- 2 carbonsboilingwithin the gasoline range which comprises subjecting the gas oil tovcracking under conditions suitable for the production of 'a extractingthe'cycle oil with a selective solvent for aromatic hydrocarbons wherebya ramnate and an extract are obtained, combining the rafilnate with theinitial gas oil to be cracked, subiecting the extract to cracking at ahigher temperature than that' maintained in the nrst cracking steptoproduce agasoline of high octane number and higher boiling hydrocarbons.and merging. the products of cracking'from'the secofcra'oking Iter."

from the first-mentioned cracking mwaanr. Y

